<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var arr1 = ['a','b'];
        var res1 = arr1.push('c','d')
        var arr2 = ['a','b'];
        var res2 = arr.shift();
        console.log(arr1);
        console.log(res1);
        console.log(arr3);
        console.log(res3);
        // 数组访问
        var arr2 = ['a','b'];
        var res3 = arr.shift();
        console.log(arr1);
        console.log(res1);
        </body>
</html>